Under Art. 82 EPC, as under R. 13.1 PCT, the application must relate to one invention only or to a group of inventions so linked as to form a single general inventive concept. The second alternative, i.e. the single-concept linked group, may give rise to a plurality of independent claims in the same or different categories (see also R. 43(2) EPC).

In W 5/92 the board considered it to be implicit in the definition of R. 13.1 PCT that the "invention" be considered in the broadest sense. Thus, according to the former PCT Search Guidelines VII-5 (PCT Gazette No. 30/1992, Sec. IV; No. 29/1993, Sec. IV), the mere fact that an international application contained claims of different categories or several independent claims of the same category was in itself no reason for objection on the grounds of lack of unity (see now guidance in para. GL/ISPE 10.01 ff. PCT International Search and Preliminary Examination Guidelines, as in force from 1.1.2019).

R. 44(1) EPC and R. 13.2 PCT provide that where a group of inventions is claimed in a European/international application, the requirement of unity of invention is fulfilled only when there is a technical relationship among those inventions involving one or more of the same or corresponding special technical features.

The former R. 30 EPC 1973 as in force until 31.5.1991, like the previous R. 13 PCT, specified the following three cases in which a combination of independent claims in different categories was to be considered as having unity in the above-mentioned sense:

(a) in addition to a claim for a given product, a claim for a process specially adapted for the manufacture of the product, and a claim for a use of the product;

(b) in addition to a claim for a given process, a claim for an apparatus or means specifically designed for carrying out the process;

(c) in addition to a claim for a given product, a claim for a process specifically adapted for the manufacture of the product, and a claim for an apparatus or means specifically designed for carrying out the process.

The list was not exhaustive and other combinations were permitted if they met the requirements of Art. 82 EPC 1973 (T 861/92). The same applied to the old version of R. 13.2 PCT (W 3/88, OJ 1990, 126; W 29/88, W 3/89). In T 702/93 it was held that this version of R. 30 EPC 1973 did not provide for such a fictitious unity in the case of independent claims in the same category.

While this fiction was removed with the amendment of R. 30 EPC 1973 and R. 13 PCT (with effect from 1.6.1991), the principles based on it, as set out in the above case law, remain unchanged (T 169/96).

In T 202/83 it was concluded from the old version of R. 30(c) EPC 1973 that the requirement of unity was not met by every subject-matter for carrying out a process. On the contrary, the provision presupposed that the means for carrying out the process had been specifically designed. Consequently, such a means in connection with the corresponding process did not meet the unity requirement if it was obvious that it could also serve to solve other technical problems.

In T 200/86 the board held that it was possible to claim, in one application, not only a product for pharmaceutical use, but also the product's non-therapeutic (cosmetic and dietary) uses.

In W 29/88 the international application related to chemical products, a process for their preparation and their use. The board was of the opinion that a particular use of a class of compounds on the one hand, and, on the other hand, a claim to that class of compounds per se or to certain members of that class of compounds could form a single general inventive concept. The board stressed that the salient point was not the identity of the respective structural scopes, but the question whether the compounds claimed per se (and the process for their manufacture) contributed to the solution of the problem underlying the use invention.

In W 32/88 (OJ 1990, 138) the board was of the opinion that an invitation to pay an additional search fee on the grounds that an international application concerning a process and an apparatus related to two different inventions, whereas the apparatus was specifically designed for carrying out the process, had no legal basis, even if the claims for the apparatus were not restricted to such use (see also W 16/89).

In W 13/89 the board found unity between a claim to the use of a substance or composition for the preparation of a medicine intended for a specific use (second medical use) and a claim to a pharmaceutical product containing that substance or composition (first medical use). This decision was confirmed in W 5/91 and W 28/91.

In W 23/91 the board confirmed the ISA's view that the novelty of a given product might justify claims of different categories being contained in a single application without contravening the requirements of unity (several new uses of the product in different areas and/or new processes concerning the product, e.g. preparation). In the case in point, the two independent product claims related to two "products", namely a nucleic acid sequence and the protein relating to the nucleic acid sequence. The board held that these products might constitute the common link if they were novel.

In W 40/92 the board took the view that there can be unity of invention if one independent claim to a process and another to the means for executing that process were comprised in one application. Said means could itself also be a process.

In T 492/91, the board found that, for the purposes of Art. 82 EPC 1973, the whole composition covered by claim 6 (new composition) need not be the product of the process according to claim 1 (process for preparing known products). It was sufficient for one component of the composition to be such a product where the composition and the process were intended to solve the same technical problem. The board concluded that the scope of claim 6 therefore did not have to be limited to the compositions resulting from the process according to claim 1, thus excluding the compositions obtainable by subsequent mixing.

In J 13/13 the Legal Board recalled that R. 43(2) EPC and R. 44 EPC govern two distinct matters: R. 43(2) EPC must be complied with even where a patent application claims and describes a group of inventions that form a single general inventive concept, while R. 44 EPC must be complied with even where only a single independent claim is drafted for each claim category.